Wireless local area networks (WLANs) have gained broad popularity. The original IEEE 802.11 WLAN standard was designed to enable communications at 1-2 Mbps in a band around 2.4 GHz. More recently, IEEE working groups have defined the 802.11a, 802.11b, 802.11e, 802.11g, 802.11n and other extensions to the original standard, in order to enable higher data rates. In the context of the present patent application and in the claims, the term “802.11” is used to refer collectively to the original IEEE 802.11 standard and all its variants and extensions, unless specifically noted otherwise.
WiMAX (Worldwide Interoperability for Microwave Access) is a new technology for wireless packet data communications, which is similar in concept to IEEE 802.11, but has a number of enhancements designed to improve performance and range. The original WiMAX standard, IEEE 802.16, specified WiMAX in the 10-66 GHz range. More recently, IEEE 802.16a added support for the 2-11 GHz range, and IEEE 802.16e (approved as IEEE 802.16-2005) extended WiMAX to mobile applications, using an enhanced orthogonal frequency division multiple access (OFDMA) modulation scheme. In the context of the present patent application and in the claims, the term “802.16” is used to refer collectively to the original IEEE 802.16 standard and all its variants and extensions, unless specifically noted otherwise.
Although there are some similarities in the physical layer interfaces (PHY) of WLAN and WIMAX systems, the medium access control (MAC) layers specified by the respective standards differ significantly. In an 802.11 WLAN, the MAC layer typically uses contention, as in Ethernet networks: Mobile stations compete for the resources of access points on a random basis. By contrast, the 802.16 MAC typically uses scheduling, in which the mobile station is allocated a time slot by the base station. The time slot can enlarge and constrict, but it remains assigned to the subscriber station, meaning that other subscribers are not supposed to use it and must take their turn.
Other broadband wireless standards are also in development. Examples include the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE), 3GPP2 Evolution-Data Optimized (EVDO) Rev C and the IEEE 802.20 High Speed Mobile Broadband Wireless Access (MBWA) specifications.